Left, right ears attuned to different sounds

Scientists in the United States have found that the right ear is better at picking up speech-like sounds and the left is more attuned to music, after studying the hearing of babies.

It has long been known that the right and left halves of the brain process sound differently.

However, those differences have been thought to stem from cellular properties unique to each brain hemisphere.

The new research suggests that the differences start at the ear.

"We always assumed that our left and right ears worked exactly the same way," lead researcher Yvonne Sininger, of the University of California, said.

"As a result, we tended to think it didn't matter which ear was impaired in a person.

"Now we see that it may have profound implications for the individual's speech and language development."

The discovery, which is described in the current issue of Science magazine, will help doctors enhance speech and language development in hearing-impaired newborns and the rehabilitation of persons with hearing loss.

Professor Sininger and her colleagues studied hearing in more than 3,000 newborns, specifically tiny amplifiers located in the outer hair cells of the inner ear.

These cells contract and expand to amplify sound vibrations, convert the vibrations to neural cells and send them to the brain.

The scientists inserted tiny probes into the babies' ears that emitted two different types of sounds and measured the amplified vibrations.

They found that speech-like clicks triggered greater amplification in the right ear, while music-like sustained tones were more greatly amplified by the left ear.

"We were intrigued to discover that the clicks triggered more amplification in the baby's right ear, while the tones induced more amplification in the baby's left ear," Professor Sininger said.

"This parallels how the brain processes speech and music, except the sides are reversed due to the brain's cross connections."